Sterilization of a large number of medical instruments and like articles must be routinely performed in health care facilities. In the past, instruments to be sterilized have typically been cleaned and wrapped in cloth or cloth-like materials prior to placement on trays for subsequent sterilization in a specially constructed steam sterilization chamber. Following sterilization, the sealed packages of instruments are stored in a "clean room" where they are considered to remain sterile for a limited and accepted period of time. Procedures such as this have been regarded as providing adequate protection against contamination for several decades.
Because of the large number of articles which must be routinely sterilized, attempts have been made to improve the efficiency of the sterilization procedure. Because the above-described wrapping technique for sterilization is both material intensive and time-consuming, sealable metal containers have been introduced for holding unwrapped instruments for sterilization and subsequent storage. However, use of such sterilization containers presents special problems which relate to the nature of the typical steam sterilization process.
During steam sterilization, articles within a sterilization chamber (an autoclave) are subjected to several distinct operational cycles. After articles to be sterilized are placed in the chamber and the chamber sealed, air is evacuated from the chamber to a desired level of vacuum, with negative pressure being maintained for aproximately one minute duration. At the conclusion of this first vacuum cycle, steam is admitted to the chamber and the temperature within the chamber is elevated, such as to a temperature on the order of approximately 270 degrees Fahrenheit. The articles in the chamber are typically subjected to this elevation in temperature for approximately six minutes. At the conclusion of this steam sterilization cycle, the supply of hot steam is turned off, and a vacuum drying cycle commenced. The vacuum applied to the chamber drives off the residual water from the steam, with the elevation of the temperature within the chamber during this vacuum drying cycle thoroughly drying the articles being sterilized. The temperature within the sterilization chamber during this second vacuum cycle is typically on the order of 270 degrees Fahrenheit, with the articles in the chamber being subjected to vacuum drying for approximately one hour. Sterilization is then complete, and the articles can be removed from the sterilization chamber for subsequent storage and use.
In order to assure proper sterilization of articles, metal containers for holding the articles during sterilization must be adapted to permit free flow of hot steam into and from the container during the steam cycle, and subsequent evacuation of air and moisture from the container during the vacuum drying cycle. In order to facilitate convenient handling and storage of the instruments after sterilization, the sterilization container is preferably arranged so that it is completely sealed against contamination at the conclusion of the sterilization process.
In the past, some metal sterilization containers have included membrane-like filters permeable to air and moisture, but impenetrable to undesired organisms and like contaminants. Such filters permit the desired communication with the interior of the container during the sterilization process. However, these types of filters must be properly fitted in order to be effective, and have proven to be prone to damage and improper installation. Additionally, such permeable filters provide no indication that the integrity of their seal has not been violated.
In view of this, it is desirable that a metal sterilization container be vacuum sealed at an appropriate point in the sterilization process in a manner which maintains the vacuum of the container during post-sterilization storage. The presence of the vacuum in the sealed container can be readily detected by an appropriate vacuum gauge on the container, and by the force required to break the vacuum accompanied by the audible inrush of air. A mechanism for sealing the sterilization container in this manner must function reliably and predictably, and must be sufficiently economical to use.
Thus, it is desirable that some type of valve mechanism be provided for the sterilization container to permit the desired communication between the interior and exterior of the container during sterilization, but which acts to permit vacuum sealing of the container against contamination at the conclusion of sterilization. Such a mechanism should preferably be relatively inexpensive and easy to use, and function predictably to assure proper sterilization of the articles. Because efficient sterilization of medical articles helps to hold down the increasing cost of health care, the introduction of an easily used, temperature responsive valve operating mechanism for sterilization containers which is economical and reliable is particularly desirable.